This invention relates generally to energy cells or batteries of small size adaptable for specialized shapes suitable for electric or electronic watches, hearing aids and the like. More particularly, this invention relates to a plastic cased cell that is sheathed in a split metal case.
Small primary energy cells used, for example, in watches and hearing aids are well known. These are generally of a circular configuration and known as "button" cells because of their shape. Such cells are generally of the alkaline type and employ metallic cases which, because of the circular shape, can be crimped or swaged around insulating intermediate members to hold the casing halves together. Examples of such cells are illustrated in U.S. Pat. No. 2,859,266 issued Nov. 1958 to Garbe and U.S. Pat. No. 3,708,343 issued Jan. 1973 to Walsh. These prior art energy cells are basically unsound because the methods of closing the cell by swaging imposes a great strain upon the separators and barriers particularly underneath the grommet. The consequence of which is that physical rupture of the cell is possible. Also, this method of closure can apply a sustained pressure on the separators so that finely divided cathode material could possibly be forced through them causing internal discharge of the cell. Further, the cell is susceptible to damage at the swage area giving rise to undesirable metallic particles hanging loosely on the cell. And, the internal grommet typically used in these type cells takes up a lot of space and screens the cathode area thereby reducing the efficiency of the cell.
It is also known to construct energy cells of plastic material and to seal plastic casing members around a peripheral flange, as shown in U.S. Pat. No. 2,966,538 issued Dec. 1962 to Bernot. Plastic cased cells are also known and described in U.S. Pat. No. 3,384,514 issued in May 1968 to Strobel.
Due to size, and shape of the internal components in devices such as hearing aids, electric watches and the like, it is sometimes desirable to have the energy cell powering the device in some other shape than the conventional circular cross section. When nonconventional shapes are employed, it becomes difficult to provide proper sealing between metallic casing members by crimping or swaging. An illustration of nonconventionally shaped nonmetallic energy cells are shown in assignees co-pending U.S. Pat. application Ser. No. 544,102 filed Jan. 27, 1975 on an invention made by R. Lewis and R. Sands.
When flanged plastic casing members are employed, difficulty may arise in providing sufficient and reliant electrical connection between a terminal of an energy cell that is readily replaceable and the casing of such devices which frequently are of metal such as the case of an electric watch. Further difficulties may also arise when the flanged energy cell is inserted into the watch, for example, by the flange getting caught on the case opening of the watch or on its movement or on its circuitry thereby possibly causing damage to the watch or to the energy cell.
Accordingly, an object of the present invention is to provide an improved energy cell casing whereby the deficiencies of the prior art energy cells are eliminated.
A further object of the present invention is to provide an improved energy cell casing wherein the electrolyte leakage path at the anode and cathode is eliminated.
A still further object of the present invention is to provide an energy cell sheathed in metal that can be molded in conventional or nonconventional shapes and provides for improved case sealing to prevent electrolyte leakage.
Another object of the present invention is to provide an improved construction for a plastic cased energy cell which can be molded in conventional or nonconventional shapes, provides an insulating seal between the casing members, is readily replaceable and provides reliable electrical connection between a terminal of the energy cell and the casing of an electric or electronic watch.
The accompanying drawings diagrammatically illustrate the embodiments of the present invention by way of example. Like numerals refer to like parts throughout.